-This Machine has a higher rate of fire, but the Brush Gun has more power. Before the patch, they would both do about the same damage per second (about 140).
-This Machine is a unique weapon that doesn't have other a non-unique variant. The Brush Gun, while very rare, also has very rare ammo. So, both guns would require keeping in good condition along with possibly spending quite a few caps.
-This Machine holds eight rounds in its enbloc clip along with having a fast reload (Brush Gun loads six rounds into a tubular magazine), but the Brush Gun has very good accuracy (This Machine has some spread to it making more suitable for mid-range combat).
Sure, one can say it's an "overpowered weapon", but one can just use a weaker weapon for more of a challenge. The thing I love about Fallout 3 and Fallout: New Vegas is you can make it a very casual game, or you can make it quite a challenging game. Besides, I'm a M1 Garand fanatic (always a favorite in just about every video game I play that has it). I'd say it's definately one of the most uber guns ever created.
Anyways, is there a very logical reason why This Machine had its power reduced?